System for supplying a fuel and working fluid mixture to a combustor

ABSTRACT

A system for supplying a working fluid to a combustor includes a combustion chamber, a liner that circumferentially surrounds at least a portion of the combustion chamber, and a flow sleeve that circumferentially surrounds at least a portion of the liner. A tube provides fluid communication for the working fluid to flow through the flow sleeve and the liner and into the combustion chamber, and the tube spirals between the flow sleeve and the liner.

FIELD OF THE INVENTION

The present invention generally involves a system for supplying aworking fluid to a combustor. In particular embodiments, the presentinvention may supply a lean fuel-air mixture to the combustion chamberthrough late lean injectors circumferentially arranged around thecombustion chamber.

BACKGROUND OF THE INVENTION

Combustors are commonly used in industrial and power generationoperations to ignite fuel to produce combustion gases having a hightemperature and pressure. For example, gas turbines typically includeone or more combustors to generate power or thrust. A typical gasturbine used to generate electrical power includes an axial compressorat the front, one or more combustors around the middle, and a turbine atthe rear. Ambient air may be supplied to the compressor, and rotatingblades and stationary vanes in the compressor progressively impartkinetic energy to the working fluid (air) to produce a compressedworking fluid at a highly energized state. The compressed working fluidexits the compressor and flows into a combustion chamber where thecompressed working fluid mixes with fuel and ignites to generatecombustion gases having a high temperature and pressure. The combustiongases expand in the turbine to produce work. For example, expansion ofthe combustion gases in the turbine may rotate a shaft connected to agenerator to produce electricity.

Various design and operating parameters influence the design andoperation of combustors. For example, higher combustion gas temperaturesgenerally improve the thermodynamic efficiency of the combustor.However, higher combustion gas temperatures also promote flashback orflame holding conditions in which the combustion flame migrates towardsthe fuel being supplied by fuel nozzles, possibly causing severe damageto the fuel nozzles in a relatively short amount of time. In addition,higher combustion gas temperatures generally increase the disassociationrate of diatomic nitrogen, increasing the production of nitrogen oxides(NO_(X)). Conversely, a lower combustion gas temperature associated withreduced fuel flow and/or part load operation (turndown) generallyreduces the chemical reaction rates of the combustion gases, increasingthe production of carbon monoxide and unburned hydrocarbons.

In a particular combustor design, one or more late lean injectors ortubes may be circumferentially arranged around the combustion chamberdownstream from the fuel nozzles. A portion of the compressed workingfluid exiting the compressor may flow through the tubes to mix with fuelto produce a lean fuel-air mixture. The lean fuel-air mixture may thenbe injected by the tubes into the combustion chamber, resulting inadditional combustion that raises the combustion gas temperature andincreases the thermodynamic efficiency of the combustor.

The late lean injectors are effective at increasing combustion gastemperatures without producing a corresponding increase in theproduction of NO_(X). However, the tubes that provide the late injectionof the lean fuel-air mixture typically have a substantially constantcross section that creates conditions around the late lean injectorssusceptible to localized flame holding. In addition, the tubes aregenerally aligned perpendicular to the flow of combustion gases in thecombustion chamber. As a result, the late lean injectors may producelarge vortices that recirculate hot combustion gases back to the surfaceof the combustion chamber, producing high thermal gradients andshortening hardware life. Therefore, an improved system for supplyingworking fluid to the combustor that reduces the conditions for flameholding and/or vortex shedding would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

One embodiment of the present invention is a system for supplying aworking fluid to a combustor. The system includes a combustion chamber,a liner that circumferentially surrounds at least a portion of thecombustion chamber, and a flow sleeve that circumferentially surroundsat least a portion of the liner. A tube provides fluid communication forthe working fluid to flow through the flow sleeve and the liner and intothe combustion chamber, and the tube spirals between the flow sleeve andthe liner.

Another embodiment of the present invention is a system for supplying aworking fluid to a combustor that includes a combustion chamber, a linerthat circumferentially surrounds at least a portion of the combustionchamber, and a flow sleeve that circumferentially surrounds at least aportion of the liner. A tube provides fluid communication through theflow sleeve and the liner and into the combustion chamber, and the tubeincludes a first side that intersects the liner at a first acute angle,a second side opposite the first side that intersects the liner at asecond angle, and the first acute angle is less than the second angle.

The present invention may also include a system for supplying a workingfluid to a combustor that includes a combustion chamber, a liner thatcircumferentially surrounds at least a portion of the combustionchamber, and a flow sleeve that circumferentially surrounds at least aportion of the liner. A tube provides fluid communication for theworking fluid to flow through the flow sleeve and the liner and into thecombustion chamber. The tube includes an ovular cross-section having alongitudinal axis, and the longitudinal axis of the ovular cross-sectionis angled with respect to a longitudinal axis of the combustion chamberas the tube passes through the liner.

Those of ordinary skill in the art will better appreciate the featuresand aspects of such embodiments, and others, upon review of thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a simplified side cross-section view of an exemplary gasturbine;

FIG. 2 is a simplified side perspective view of a portion of thecombustor shown in FIG. 1 according to a first embodiment of the presentinvention;

FIG. 3 is an enlarged side perspective view of the late lean injectorshown in FIG. 2;

FIG. 4 is an enlarged side cross-section view of the late lean injectorshown in FIG. 2; and

FIG. 5 is a plan view of the late lean injector shown in FIG. 2 frominside the combustion chamber.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of theinvention, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the invention. As used herein, theterms “first”, “second”, and “third” may be used interchangeably todistinguish one component from another and are not intended to signifylocation or importance of the individual components. In addition, theterms “upstream” and “downstream” refer to the relative location ofcomponents in a fluid pathway. For example, component A is upstream fromcomponent B if a fluid flows from component A to component B.Conversely, component B is downstream from component A if component Breceives a fluid flow from component A.

Each example is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that modifications and variations can be made in thepresent invention without departing from the scope or spirit thereof.For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present invention covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

Various embodiments of the present invention include a system forsupplying a working fluid to a combustor. The system generally includesone or more late lean injectors circumferentially arranged around acombustion chamber to inject a lean mixture of fuel and working fluidinto the combustion chamber. In particular embodiments, the late leaninjectors may have various geometric profiles to enhance injection ofthe lean mixture into the combustion chamber without increasing flameholding and/or vortex shedding. For example, the late lean injectors mayinclude a spiraling profile, a tapered cross-section, and/or an ovularcross-section. Although exemplary embodiments of the present inventionwill be described generally in the context of a combustor incorporatedinto a gas turbine for purposes of illustration, one of ordinary skillin the art will readily appreciate that embodiments of the presentinvention may be applied to any combustor and are not limited to a gasturbine combustor unless specifically recited in the claims.

FIG. 1 provides a simplified cross-section view of an exemplary gasturbine 10 incorporating one embodiment of the present invention. Asshown, the gas turbine 10 may include a compressor 12 at the front, oneor more combustors 14 radially disposed around the middle, and a turbine16 at the rear. The compressor 12 and the turbine 16 typically share acommon rotor 18 connected to a generator 20 to produce electricity.

The compressor 12 may be an axial flow compressor in which a workingfluid 22, such as ambient air, enters the compressor 12 and passesthrough alternating stages of stationary vanes 24 and rotating blades26. A compressor casing 28 contains the working fluid 22 as thestationary vanes 24 and rotating blades 26 accelerate and redirect theworking fluid 22 to produce a continuous flow of compressed workingfluid 22. The majority of the compressed working fluid 22 flows througha compressor discharge plenum 30 to the combustor 14.

The combustor 14 may be any type of combustor known in the art. Forexample, as shown in FIG. 1, a combustor casing 32 may circumferentiallysurround some or all of the combustor 14 to contain the compressedworking fluid 22 flowing from the compressor 12. One or more fuelnozzles 34 may be radially arranged in an end cover 36 to supply fuel toa combustion chamber 38 downstream from the fuel nozzles 34. Possiblefuels include, for example, one or more of blast furnace gas, coke ovengas, natural gas, vaporized liquefied natural gas (LNG), hydrogen, andpropane. The compressed working fluid 22 may flow from the compressordischarge plenum 30 along the outside of the combustion chamber 38before reaching the end cover 36 and reversing direction to flow throughthe fuel nozzles 34 to mix with the fuel. The mixture of fuel andcompressed working fluid 22 flows into the combustion chamber 38 whereit ignites to generate combustion gases having a high temperature andpressure. The combustion gases flow through a transition piece 40 to theturbine 16.

The turbine 16 may include alternating stages of stators 42 and rotatingbuckets 44. The first stage of stators 42 redirects and focuses thecombustion gases onto the first stage of rotating buckets 44. As thecombustion gases pass over the first stage of rotating buckets 44, thecombustion gases expand, causing the rotating buckets 44 and rotor 18 torotate. The combustion gases then flow to the next stage of stators 42which redirects the combustion gases to the next stage of rotatingbuckets 44, and the process repeats for the following stages.

FIG. 2 provides a simplified perspective view of a portion of thecombustor 14 shown in FIG. 1 according to a first embodiment of thepresent invention. As shown, the combustor 14 may include a liner 46that circumferentially surrounds at least a portion of the combustionchamber 38, and a flow sleeve 48 may circumferentially surround theliner 46 to define an annular passage 50 that surrounds the liner 46. Inthis manner, the compressed working fluid 22 from the compressordischarge plenum 30 may flow through the annular passage 50 along theoutside of the liner 46 to provide convective cooling to the liner 46before reversing direction to flow through the fuel nozzles 34 (shown inFIG. 1) and into the combustion chamber 38.

The combustor 14 may further include a plurality of late lean injectorsor tubes 60 that may provide a late lean injection of fuel andcompressed working fluid 22 into the combustion chamber 38. The tubes 60may be circumferentially arranged around the combustion chamber 38,liner 46, and flow sleeve 48 downstream from the fuel nozzles 34 toprovide fluid communication for the compressed working fluid 22 to flowthrough the flow sleeve 48 and the liner 46 and into the combustionchamber 38. As shown in FIG. 2, the flow sleeve 48 may include aninternal fuel passage 62, and each tube 60 may include one or more fuelports 64 circumferentially arranged around the tube 60. In this manner,the fuel passage 62 may provide fluid communication for fuel to flowthrough the fuel ports 64 and into the tubes 60. The tubes 60 mayreceive the same or a different fuel than supplied to the fuel nozzles34 and mix the fuel with a portion of the compressed working fluid 22before or while injecting the mixture into the combustion chamber 38. Inthis manner, the tubes 60 may supply a lean mixture of fuel andcompressed working fluid 22 for additional combustion to raise thetemperature, and thus the efficiency, of the combustor 14.

FIGS. 3-5 provide enlarged perspective, cross-section, and plan views ofthe tubes 60 to illustrate various features and combinations of featuresthat may be present in various embodiments of the tubes 60 within thescope of the present invention. For example, FIG. 3 provides an enlargedperspective view of the tube 60 shown in FIG. 2 to more clearlyillustrate the shape and curvature of the tube 60 between the flowsleeve 48 and the liner 46 in one particular embodiment. As shown inFIG. 3, the tube 60 may include an elliptical cross-section 70 having alongitudinal axis 72. In addition, the longitudinal axis 72 of the tube60 may spiral completely or partially between the flow sleeve 48 and theliner 46. The amount of spiraling will vary according to particularembodiments. For example, the longitudinal axis 72 may rotate up to 80degrees or more in particular embodiments, depending on the distancebetween the flow sleeve 48 and the liner 46, the internal volume of theparticular tube 60, the length of the longitudinal axis 72, and/or otherdesign considerations. It is anticipated that the combination of theelliptical shape and spiraling will reduce pressure loss of thecompressed working fluid 22 flowing through the tubes 60 and/or enhancemixing of the lean fuel-working fluid mixture with the combustion gases.

FIG. 4 provides an enlarged side cross-section view of the tube 60 shownin FIG. 2 to illustrate that the tube 60 may include a tapered end 74that passes through the liner 46. For example, the tapered end 74 mayreduce the cross-sectional area of the tube by 2-50 percent or more atthe intersection of the liner 46 to accelerate the fluid injection intothe combustion chamber 38 and reduce the occurrence of flame holdingand/or flash back near the tubes 60. In particular embodiments, thetapered end 74 may be symmetric or asymmetric. For example, as shown inFIG. 4, the tapered end 74 may include a first side 76 that intersectsthe liner 46 at a first acute angle 78, a second side 80 opposite thefirst side 76 that intersects the liner 46 at a second angle 82. Forconsistency and convention, the first acute angle 78 and the secondangel 82 are measured at the intersection of the first and second sides76, 80, respectively, with the liner 46 from the outside of the tube 60.The first acute angle 78 may be, for example, 2-25 degrees, depending onthe particular embodiment, and the first acute angle 78 may be less thanthe second angle 82. The resulting asymmetry at the tapered end 74 maynot only accelerate the fluid injection into the combustion chamber 38,but it may also reduce vortex shedding and the associated recirculationof hot combustion gases near the liner 46 created by the injected fluid.

FIG. 5 provides a plan view of the tube 60 shown in FIG. 2 from insidethe combustion chamber 38. As shown, the longitudinal axis 72 of theovular cross-section 70 may be angled with respect to a longitudinalaxis 84 of the combustion chamber 38 as the tube 60 passes through theliner 46. As a result, particularly when combined with the spiralingfeature shown in FIG. 3 and/or the tapered end 74 shown in FIG. 4, theinjected lean fuel-working fluid mixture may penetrate further into thecombustion chamber 38 to enhance mixing between the combustion gases andthe injected fluids.

One of ordinary skill in the art will readily appreciate from theteachings herein that the tubes 60 shown in FIG. 2 may include only oneor more than one of the features described and illustrated in moredetail in FIGS. 3-5, and embodiments of the present invention are notlimited to any combination of such features unless specifically recitedin the claims. In addition, the particular embodiments shown anddescribed with respect to FIGS. 1-5 may also provide a method forsupplying the working fluid 22 to the combustor 14. The method mayinclude flowing the working fluid 22 from the compressor 12 through thecombustion chamber 38 and diverting or flowing a portion of the workingfluid 22 through the tubes 60 circumferentially arranged around thecombustion chamber 38. In particular embodiments, the method may furtherinclude spiraling and/or accelerating the diverted portion of theworking fluid 22 inside the tubes 60 prior to injection into thecombustion chamber 38. The various features of the tubes 60 describedherein may thus reduce the conditions conducive to flame holding nearthe tubes 60, reduce vortex shedding and recirculation zones near thetubes 60, and/or enhance fluid penetration and mixing inside thecombustion chamber 38 to enhance NOx reduction.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A system for supplying a working fluid to acombustor, comprising: a. a combustion chamber; b. a liner thatcircumferentially surrounds at least a portion of the combustionchamber; c. a flow sleeve having an inner sleeve that circumferentiallysurrounds at least a portion of the liner, an outer sleeve thatcircumferentially surrounds the inner sleeve and a fuel passage definedby and between the inner and outer sleeves; d. a tube that providesfluid communication for the working fluid to flow through the flowsleeve and the liner and into the combustion chamber, wherein the tubespirals between the flow sleeve and the liner; and e. a plurality offuel ports circumferentially arranged around an inlet of the tube,wherein each fuel port is in fluid communication with the fuel passage.2. The system as in claim 1, wherein the tube comprises a tapered endthat passes through the liner.
 3. The system as in claim 2, wherein thetapered end is asymmetric.
 4. The system as in claim 2, wherein thetapered end comprises a first side that intersects the liner at a firstacute angle, a second side opposite the first side that intersects theliner at a second angle, and the first acute angle is less than thesecond angle.
 5. The system as in claim 1, wherein the tube comprises anelliptical cross-section having a longitudinal axis.
 6. The system as inclaim 5, wherein the longitudinal axis of the elliptical cross-sectionis angled with respect to a longitudinal axis of the combustion chamberas the tube passes through the liner.
 7. The system as in claim 1,wherein the tube comprises a tapered end that passes through the linerand an elliptical cross-section having a longitudinal axis.
 8. A systemfor supplying a working fluid to a combustor, comprising: a. acombustion chamber; b. a liner that circumferentially surrounds at leasta portion of the combustion chamber; c. a flow sleeve having an innersleeve that circumferentially surrounds at least a portion of the liner,an outer sleeve that circumferentially surrounds the inner sleeve and afuel passage defined by and between the inner and outer sleeves; d. atube that provides fluid communication through the flow sleeve and theliner and into the combustion chamber, wherein the tube comprises afirst side that intersects the liner at a first acute angle, a secondside opposite the first side that intersects the liner at a secondangle, and the first acute angle is less than the second angle; and e. aplurality of fuel ports circumferentially arranged around an inlet ofthe tube, wherein each fuel port is in fluid communication with the fuelpassage.
 9. The system as in claim 8, wherein the tube spirals betweenthe flow sleeve and the liner.
 10. The system as in claim 8, wherein thetube comprises an elliptical cross-section having a longitudinal axis.11. The system as in claim 10, wherein the longitudinal axis of theelliptical cross-section is angled with respect to a longitudinal axisof the combustion chamber as the tube passes through the liner.
 12. Thesystem as in claim 8, wherein the tube comprises an ellipticalcross-section having a longitudinal axis that spirals between the flowsleeve and the liner.
 13. A system for supplying a working fluid to acombustor, comprising: a. a combustion chamber; b. a liner thatcircumferentially surrounds at least a portion of the combustionchamber; c. a flow sleeve having an inner sleeve that circumferentiallysurrounds at least a portion of the liner, an outer sleeve thatcircumferentially surrounds the inner sleeve and a fuel passage definedby and between the inner and outer sleeves; d. a tube that providesfluid communication for the working fluid to flow through the flowsleeve and the liner and into the combustion chamber, wherein the tubecomprises an elliptical cross-section having a longitudinal axis, andthe longitudinal axis of the elliptical cross-section is angled withrespect to a longitudinal axis of the combustion chamber as the tubepasses through the liner; and e. a plurality of fuel portscircumferentially arranged around an inlet of the tube, wherein eachfuel port is in fluid communication with the fuel passage.
 14. Thesystem as in claim 13, wherein the tube spirals between the flow sleeveand the liner.
 15. The system as in claim 13, wherein the tube comprisesa tapered end that passes through the liner.
 16. The system as in claim15, wherein the tapered end comprises a first side that intersects theliner at a first acute angle, a second side opposite the first side thatintersects the liner at a second angle, and the first acute angle isless than the second angle.